1. Field of the Invention
The present invention relates to an X-ray tube for generating X-rays.
2. Related Background Art
In an X-ray tube, a cathode is heated in a high-vacuum tube to emit electrons, and the electrons are bombarded against an anode target to which a high voltage is applied, thereby generating X-rays. X-ray tubes with various structures are available depending on applications. A predetermined voltage must be supplied to the tube from the outside in order to apply a voltage to a heater, grid electrode, and the like. For this purpose, as described in Japanese Utility Model Laid-Open No. 5-11302 and Japanese Patent Laid-Open Nos. 9-180630 and 9-180660, a plurality of pins made of a conductor extend through an insulating stem, and a predetermined voltage is supplied into the tube of the X-ray tube through them.
In the X-ray tube described above, insulation among the pins is impaired by long-time use, and the operation of the X-ray tube accordingly becomes unstable. It is, therefore, an object of the present invention to provide an X-ray tube in which the above problem is solved and which operates stably even after long-time use.
In order to solve the above problem, according to the present invention, there is provided an X-ray tube in which a cathode is heated to emit electrons, and the electrons are bombarded against an anode target, thereby generating X-rays, characterized by comprising an insulating substrate mounted on an opening portion of a container housing the cathode, a plurality of pins extending through the insulating substrate and adapted to supply a voltage into the container, and pin covers mounted on the pins in the container and arranged at positions away from a surface of the insulating substrate to cover base portions of the pins.
With the present invention, even when the heater, cathode, and the like heated to a high temperature produce conductive debris due to long-time use, the debris does not attach to the base portions of the pins because of the presence of the pin covers. Accordingly, even if the debris attaches to the surface of the insulating substrate, it does not impair insulation among the pins. Thus, even after long-time use, the X-ray tube can operate stably without being adversely affected by the debris generated by the usage.